revamping building from WSL

.efrocachemap

@@ -4061,26 +4061,26 @@
   "build/assets/windows/Win32/ucrtbased.dll": "2def5335207d41b21b9823f6805997f1",
   "build/assets/windows/Win32/vc_redist.x86.exe": "b08a55e2e77623fe657bea24f223a3ae",
   "build/assets/windows/Win32/vcruntime140d.dll": "865b2af4d1e26a1a8073c89acb06e599",
-  "build/prefab/full/linux_arm64_gui/debug/ballisticakit": "ae5d54179a3a0fae2de63332844033ad",
+  "build/prefab/full/linux_arm64_gui/debug/ballisticakit": "e02d676254f37e6a6bfc2d992832edc7",
-  "build/prefab/full/linux_arm64_gui/release/ballisticakit": "6ee081b61d4f2fdbd93486ded4f9a64c",
+  "build/prefab/full/linux_arm64_gui/release/ballisticakit": "b6aae173f0657f98481ad513d9d4cbd5",
-  "build/prefab/full/linux_arm64_server/debug/dist/ballisticakit_headless": "e7407d776c2109ff69a3cb5ba7ee96e3",
+  "build/prefab/full/linux_arm64_server/debug/dist/ballisticakit_headless": "35fb45c3895174231254aa97ff2d43e5",
-  "build/prefab/full/linux_arm64_server/release/dist/ballisticakit_headless": "31a2f27c9f96e6514546c2c287e2b02a",
+  "build/prefab/full/linux_arm64_server/release/dist/ballisticakit_headless": "f7bb6bcc1884a692e03f52c58d83bc89",
-  "build/prefab/full/linux_x86_64_gui/debug/ballisticakit": "afe92df503843db897e9d352f0f9d15d",
+  "build/prefab/full/linux_x86_64_gui/debug/ballisticakit": "42b848cb83e3fee4a56b0f24901c1423",
-  "build/prefab/full/linux_x86_64_gui/release/ballisticakit": "1c195ea2f0436b0857bcf1f53596c9ed",
+  "build/prefab/full/linux_x86_64_gui/release/ballisticakit": "0af09f79ae95b7d31229e62ef925c283",
-  "build/prefab/full/linux_x86_64_server/debug/dist/ballisticakit_headless": "cebf710fd74b426078849cfb61ddfe05",
+  "build/prefab/full/linux_x86_64_server/debug/dist/ballisticakit_headless": "1babb2d89a351a48c1318515b23fb256",
-  "build/prefab/full/linux_x86_64_server/release/dist/ballisticakit_headless": "70444645dab4201857c281df50c7fbab",
+  "build/prefab/full/linux_x86_64_server/release/dist/ballisticakit_headless": "0ed1b2deda022680096fcc185437b2f5",
-  "build/prefab/full/mac_arm64_gui/debug/ballisticakit": "da829cffaeba3688c086706201f3cd9c",
+  "build/prefab/full/mac_arm64_gui/debug/ballisticakit": "e3b96fd440e737d7ee9588aa5517a270",
-  "build/prefab/full/mac_arm64_gui/release/ballisticakit": "3c3dc389b03a8f6b79c0e1cbb5d57c28",
+  "build/prefab/full/mac_arm64_gui/release/ballisticakit": "345a3346b1b3b28932b9fc3b6802ba58",
-  "build/prefab/full/mac_arm64_server/debug/dist/ballisticakit_headless": "f4d13a59defe384f095d39c0b8fa0b93",
+  "build/prefab/full/mac_arm64_server/debug/dist/ballisticakit_headless": "c4cfd2482416cf9a71a3dcb283dc06cc",
-  "build/prefab/full/mac_arm64_server/release/dist/ballisticakit_headless": "281d39c45a22a27a5f936901ad24ad83",
+  "build/prefab/full/mac_arm64_server/release/dist/ballisticakit_headless": "af6c9def782a7be317a247b0294d2577",
-  "build/prefab/full/mac_x86_64_gui/debug/ballisticakit": "04a4ee3d2743618f2742e68d715864b3",
+  "build/prefab/full/mac_x86_64_gui/debug/ballisticakit": "6537ce8b82230275d3baa495f0b087e2",
-  "build/prefab/full/mac_x86_64_gui/release/ballisticakit": "046391bb7ddf1a3e76c07a0299211572",
+  "build/prefab/full/mac_x86_64_gui/release/ballisticakit": "18c6239b2284547be3f354a9ab74f65c",
-  "build/prefab/full/mac_x86_64_server/debug/dist/ballisticakit_headless": "5fe069c4c2f38d8bf5ab7cc90b8719ee",
+  "build/prefab/full/mac_x86_64_server/debug/dist/ballisticakit_headless": "a53872e247c56e1d297c8fc227ad38e9",
-  "build/prefab/full/mac_x86_64_server/release/dist/ballisticakit_headless": "09bd3c5237d9cc020c805252470a05f5",
+  "build/prefab/full/mac_x86_64_server/release/dist/ballisticakit_headless": "38607776459217d77b60417a5a9a5fbe",
-  "build/prefab/full/windows_x86_gui/debug/BallisticaKit.exe": "abeb51f519cdfc31a00630d5f90c2b87",
+  "build/prefab/full/windows_x86_gui/debug/BallisticaKit.exe": "fb23a676c5e53441a101499801c5e0ee",
-  "build/prefab/full/windows_x86_gui/release/BallisticaKit.exe": "45872369ead35cd0702f645cb0290687",
+  "build/prefab/full/windows_x86_gui/release/BallisticaKit.exe": "3bf6afb5a18a95b7a7d7286c6dcc106c",
-  "build/prefab/full/windows_x86_server/debug/dist/BallisticaKitHeadless.exe": "d296df575fcbbc4c0d9d10390279b981",
+  "build/prefab/full/windows_x86_server/debug/dist/BallisticaKitHeadless.exe": "8b0d174baa273f6d7921e067fae3316a",
-  "build/prefab/full/windows_x86_server/release/dist/BallisticaKitHeadless.exe": "ab42d76f9ce4d01e84d7b4af20f83a9f",
+  "build/prefab/full/windows_x86_server/release/dist/BallisticaKitHeadless.exe": "2f37b65edd1c4eca4c2dd32506977696",
   "build/prefab/lib/linux_arm64_gui/debug/libballisticaplus.a": "d9865523059d8cf11b2bef4b9da9a8c9",
   "build/prefab/lib/linux_arm64_gui/release/libballisticaplus.a": "56d6440f62c271c4ce9ef520400395a3",
   "build/prefab/lib/linux_arm64_server/debug/libballisticaplus.a": "d9865523059d8cf11b2bef4b9da9a8c9",
@@ -4097,14 +4097,14 @@
   "build/prefab/lib/mac_x86_64_gui/release/libballisticaplus.a": "c2cf0dc227e41a826c913d12e117c316",
   "build/prefab/lib/mac_x86_64_server/debug/libballisticaplus.a": "fbdc80e41c5883b4a893d2f0786e377f",
   "build/prefab/lib/mac_x86_64_server/release/libballisticaplus.a": "c2cf0dc227e41a826c913d12e117c316",
-  "build/prefab/lib/windows/Debug_Win32/BallisticaKitGenericPlus.lib": "85e804e02022cf07b5cf6e9024b66b71",
+  "build/prefab/lib/windows/Debug_Win32/BallisticaKitGenericPlus.lib": "403d99152d4610ad11ea524772a84ca3",
-  "build/prefab/lib/windows/Debug_Win32/BallisticaKitGenericPlus.pdb": "8477e27bd6da06fd0cc390aa9b2d49eb",
+  "build/prefab/lib/windows/Debug_Win32/BallisticaKitGenericPlus.pdb": "ce022601dc7ce016fe11ed5092534672",
-  "build/prefab/lib/windows/Debug_Win32/BallisticaKitHeadlessPlus.lib": "75c2eea1899eb33777c323165e766022",
+  "build/prefab/lib/windows/Debug_Win32/BallisticaKitHeadlessPlus.lib": "e45a094dba08254cf1ba50bf435f5e8d",
-  "build/prefab/lib/windows/Debug_Win32/BallisticaKitHeadlessPlus.pdb": "6dc94f266087d91a399825a57f3fef23",
+  "build/prefab/lib/windows/Debug_Win32/BallisticaKitHeadlessPlus.pdb": "ea38b10f23c2791d92696f17b53f8fa7",
-  "build/prefab/lib/windows/Release_Win32/BallisticaKitGenericPlus.lib": "43d912d3b4026d32b9c3fb08481684b1",
+  "build/prefab/lib/windows/Release_Win32/BallisticaKitGenericPlus.lib": "5ee3cbfcce6b6cd9bdaf8239c3b78d0d",
-  "build/prefab/lib/windows/Release_Win32/BallisticaKitGenericPlus.pdb": "d2a64a9724333ccbd32df8a9c8a1c2f8",
+  "build/prefab/lib/windows/Release_Win32/BallisticaKitGenericPlus.pdb": "aa3b5bd935d8593611f13108af5d9633",
-  "build/prefab/lib/windows/Release_Win32/BallisticaKitHeadlessPlus.lib": "c13bed7154fdc3e1a83ffcea5756a375",
+  "build/prefab/lib/windows/Release_Win32/BallisticaKitHeadlessPlus.lib": "1104c4f10bbe25539c1b4e38ba041375",
-  "build/prefab/lib/windows/Release_Win32/BallisticaKitHeadlessPlus.pdb": "02e9a86205d9549484c2f5d9a3eaebe8",
+  "build/prefab/lib/windows/Release_Win32/BallisticaKitHeadlessPlus.pdb": "aa0c1c558389babcaa2166ef9ae4bad0",
   "src/assets/ba_data/python/babase/_mgen/__init__.py": "f885fed7f2ed98ff2ba271f9dbe3391c",
   "src/assets/ba_data/python/babase/_mgen/enums.py": "b611c090513a21e2fe90e56582724e9d",
   "src/ballistica/base/mgen/pyembed/binding_base.inc": "72bfed2cce8ff19741989dec28302f3f",

CHANGELOG.md

@@ -1,4 +1,4 @@
-### 1.7.33 (build 21779, api 8, 2024-03-13)
+### 1.7.33 (build 21785, api 8, 2024-03-14)
 - Stress test input-devices are now a bit smarter; they won't press any buttons
   while UIs are up (this could cause lots of chaos if it happened).
 - Added a 'Show Demos When Idle' option in advanced settings. If enabled, the

Makefile

@@ -210,37 +210,50 @@ pcommandbatch_speed_test: prereqs
 
 # Prebuilt binaries for various platforms.
 
+# WSL is Linux but running under Windows, so it can target either. By default
+# we want it to yield Windows native builds for these prefab targets but this
+# env var can be set to change that.
+BA_WSL_TARGETS_WINDOWS ?= 1
+
 # Assemble & run a gui debug build for this platform.
 prefab-gui-debug: prefab-gui-debug-build
-	$($(shell $(PCOMMAND) prefab_run_var gui-debug))
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ $($(shell $(PCOMMAND) prefab_run_var gui-debug))
 
 # Assemble & run a gui release build for this platform.
 prefab-gui-release: prefab-gui-release-build
-	$($(shell $(PCOMMAND) prefab_run_var gui-release))
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ $($(shell $(PCOMMAND) prefab_run_var gui-release))
 
 # Assemble a debug build for this platform.
 prefab-gui-debug-build:
-	@$(PCOMMAND) make_prefab gui-debug
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ @$(PCOMMAND) make_prefab gui-debug
 
 # Assemble a release build for this platform.
 prefab-gui-release-build:
-	@$(PCOMMAND) make_prefab gui-release
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ @$(PCOMMAND) make_prefab gui-release
 
 # Assemble & run a server debug build for this platform.
 prefab-server-debug: prefab-server-debug-build
-	$($(shell $(PCOMMAND) prefab_run_var server-debug))
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ $($(shell $(PCOMMAND) prefab_run_var server-debug))
 
 # Assemble & run a server release build for this platform.
 prefab-server-release: prefab-server-release-build
-	$($(shell $(PCOMMAND) prefab_run_var server-release))
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ $($(shell $(PCOMMAND) prefab_run_var server-release))
 
 # Assemble a server debug build for this platform.
 prefab-server-debug-build:
-	@$(PCOMMAND) make_prefab server-debug
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ @$(PCOMMAND) make_prefab server-debug
 
 # Assemble a server release build for this platform.
 prefab-server-release-build:
-	@$(PCOMMAND) make_prefab server-release
+	BA_WSL_TARGETS_WINDOWS=$(BA_WSL_TARGETS_WINDOWS) \
+ @$(PCOMMAND) make_prefab server-release
 
 # Clean all prefab builds.
 prefab-clean:

src/assets/ba_data/python/baenv.py

@@ -52,7 +52,7 @@ if TYPE_CHECKING:
 
 # Build number and version of the ballistica binary we expect to be
 # using.
-TARGET_BALLISTICA_BUILD = 21779
+TARGET_BALLISTICA_BUILD = 21785
 TARGET_BALLISTICA_VERSION = '1.7.33'
 
 

src/ballistica/shared/ballistica.cc

@@ -39,7 +39,7 @@ auto main(int argc, char** argv) -> int {
 namespace ballistica {
 
 // These are set automatically via script; don't modify them here.
-const int kEngineBuildNumber = 21779;
+const int kEngineBuildNumber = 21785;
 const char* kEngineVersion = "1.7.33";
 const int kEngineApiVersion = 8;
 

tools/batools/build.py

@@ -76,6 +76,87 @@ class PrefabTarget(Enum):
     GUI_RELEASE = 'gui-release'
     SERVER_RELEASE = 'server-release'
 
+    @property
+    def buildtype(self) -> str:
+        """Return the build type for this target."""
+        return self.value.split('-')[0]
+
+    @property
+    def buildmode(self) -> str:
+        """Return the build mode for this target."""
+        return self.value.split('-')[1]
+
+
+class PrefabPlatform(Enum):
+    """Distinct os/cpu-arch/etc. combos we support for prefab builds."""
+
+    MAC_X86_64 = 'mac_x86_64'
+    MAC_ARM64 = 'mac_arm64'
+    WINDOWS_X86 = 'windows_x86'
+    LINUX_X86_64 = 'linux_x86_64'
+    LINUX_ARM64 = 'linux_arm64'
+
+    @classmethod
+    def get_current(
+        cls, wsl_targets_windows: bool | None = None
+    ) -> PrefabPlatform:
+        """Get an identifier for the platform running this build.
+
+        Pass a bool `wsl_targets_windows` value to cause WSL to target
+        either native Windows (True) or Linux (False). If this value is
+        not passed, the env var BA_WSL_TARGETS_WINDOWS is used, and if that
+        is not set, the default is False (Linux builds).
+
+        Throws a RuntimeError on unsupported platforms.
+        """
+        import platform
+
+        if wsl_targets_windows is None:
+            wsl_targets_windows = (
+                os.environ.get('BA_WSL_TARGETS_WINDOWS', '0') == '1'
+            )
+
+        system = platform.system()
+        machine = platform.machine()
+
+        if system == 'Darwin':
+            if machine == 'x86_64':
+                return cls.MAC_X86_64
+            if machine == 'arm64':
+                return cls.MAC_ARM64
+            raise RuntimeError(
+                f'PrefabPlatform.get_current:'
+                f' unsupported mac machine type:'
+                f' {machine}.'
+            )
+        if system == 'Linux':
+            # If it looks like we're in Windows Subsystem for Linux, we may
+            # want to operate on Windows versions.
+            if wsl_targets_windows:
+                if 'microsoft' in platform.uname().release.lower():
+                    if machine == 'x86_64':
+                        # Currently always targeting 32 bit for prefab stuff.
+                        return cls.WINDOWS_X86
+                    # TODO: add support for arm windows
+                    raise RuntimeError(
+                        f'make_prefab: unsupported win machine type: {machine}.'
+                    )
+
+            if machine == 'x86_64':
+                return cls.LINUX_X86_64
+            if machine == 'aarch64':
+                return cls.LINUX_ARM64
+            raise RuntimeError(
+                f'PrefabPlatform.get_current:'
+                f' unsupported linux machine type:'
+                f' {machine}.'
+            )
+        raise RuntimeError(
+            f'PrefabPlatform.get_current:'
+            f' unrecognized platform:'
+            f' {platform.system()}.'
+        )
+
 
 class LazyBuildCategory(Enum):
     """Types of sources."""
@@ -296,49 +377,6 @@ def archive_old_builds(
         )
 
 
-def get_current_prefab_platform(wsl_gives_windows: bool = True) -> str:
-    """Get an identifier for the platform running this build.
-
-    Throws a RuntimeError on unsupported platforms.
-    """
-    import platform
-
-    system = platform.system()
-    machine = platform.machine()
-
-    if system == 'Darwin':
-        if machine == 'x86_64':
-            return 'mac_x86_64'
-        if machine == 'arm64':
-            return 'mac_arm64'
-        raise RuntimeError(
-            f'make_prefab: unsupported mac machine type:' f' {machine}.'
-        )
-    if system == 'Linux':
-        # If it looks like we're in Windows Subsystem for Linux,
-        # we may want to operate on Windows versions.
-        if wsl_gives_windows:
-            if 'microsoft' in platform.uname().release.lower():
-                if machine == 'x86_64':
-                    # Currently always targeting 32 bit for prefab stuff.
-                    return 'windows_x86'
-                # TODO: add support for arm windows
-                raise RuntimeError(
-                    f'make_prefab: unsupported win machine type: {machine}.'
-                )
-
-        if machine == 'x86_64':
-            return 'linux_x86_64'
-        if machine == 'aarch64':
-            return 'linux_arm64'
-        raise RuntimeError(
-            f'make_prefab: unsupported linux machine type:' f' {machine}.'
-        )
-    raise RuntimeError(
-        f'make_prefab: unrecognized platform:' f' {platform.system()}.'
-    )
-
-
 def _vstr(nums: Sequence[int]) -> str:
     return '.'.join(str(i) for i in nums)
 

tools/batools/pcommands.py

@@ -616,60 +616,80 @@ def ensure_prefab_platform() -> None:
     the prefab platform may be Windows; not Linux. Also, a 64-bit
     os may be targeting a 32-bit platform.
     """
-    import batools.build
     from efro.error import CleanError
 
+    from batools.build import PrefabPlatform
+
     args = pcommand.get_args()
     if len(args) != 1:
         raise CleanError('Expected 1 platform name arg.')
-    needed = args[0]
+    needed = PrefabPlatform(args[0])
-    current = batools.build.get_current_prefab_platform()
+    current = PrefabPlatform.get_current()
-    if current != needed:
+    if current is not needed:
         raise CleanError(
-            f'Incorrect platform: we are {current}, this requires {needed}.'
+            f'Incorrect platform: we are {current.value},'
+            f' this requires {needed.value}.'
         )
 
 
 def prefab_run_var() -> None:
     """Print the current platform prefab run target var."""
-    import batools.build
+    from batools.build import PrefabPlatform
 
     args = pcommand.get_args()
     if len(args) != 1:
         raise RuntimeError('Expected 1 arg.')
     base = args[0].replace('-', '_').upper()
-    platform = batools.build.get_current_prefab_platform().upper()
+    platform = PrefabPlatform.get_current().value.upper()
     pcommand.clientprint(f'RUN_PREFAB_{platform}_{base}', end='')
 
 
 def prefab_binary_path() -> None:
-    """Print the current platform prefab binary path."""
+    """Print the path to the current prefab binary."""
-    import batools.build
+    from typing import assert_never
+
+    from efro.error import CleanError
+
+    from batools.build import PrefabPlatform, PrefabTarget
 
     pcommand.disallow_in_batch()
 
     if len(sys.argv) != 3:
-        raise RuntimeError('Expected 1 arg.')
+        options = ', '.join(t.value for t in PrefabTarget)
-    buildtype, buildmode = sys.argv[2].split('-')
+        raise CleanError(f'Expected 1 PrefabTarget arg. Options are {options}.')
-    platform = batools.build.get_current_prefab_platform()
 
-    if platform.startswith('windows_'):
+    target = PrefabTarget(sys.argv[2])
+
+    buildtype = target.buildtype
+    buildmode = target.buildmode
+
+    platform = PrefabPlatform.get_current()
+
+    if platform is PrefabPlatform.WINDOWS_X86:
         if buildtype == 'gui':
             binpath = 'BallisticaKit.exe'
         elif buildtype == 'server':
             binpath = 'dist/BallisticaKitHeadless.exe'
         else:
             raise ValueError(f"Invalid buildtype '{buildtype}'.")
-    else:
+    elif (
+        platform is PrefabPlatform.MAC_ARM64
+        or platform is PrefabPlatform.MAC_X86_64
+        or platform is PrefabPlatform.LINUX_ARM64
+        or platform is PrefabPlatform.LINUX_X86_64
+    ):
         if buildtype == 'gui':
             binpath = 'ballisticakit'
         elif buildtype == 'server':
             binpath = 'dist/ballisticakit_headless'
         else:
             raise ValueError(f"Invalid buildtype '{buildtype}'.")
+    else:
+        # Make sure we're covering all options.
+        assert_never(platform)
 
     print(
-        f'build/prefab/full/{platform}_{buildtype}/{buildmode}/{binpath}',
+        f'build/prefab/full/{platform.value}_{buildtype}/{buildmode}/{binpath}',
         end='',
     )
 
@@ -677,20 +697,20 @@ def prefab_binary_path() -> None:
 def make_prefab() -> None:
     """Run prefab builds for the current platform."""
     import subprocess
-    import batools.build
+    from batools.build import PrefabPlatform, PrefabTarget
 
     pcommand.disallow_in_batch()
 
     if len(sys.argv) != 3:
         raise RuntimeError('Expected one argument')
-    target = batools.build.PrefabTarget(sys.argv[2])
+    targetstr = PrefabTarget(sys.argv[2]).value
-    platform = batools.build.get_current_prefab_platform()
+    platformstr = PrefabPlatform.get_current().value
 
     # We use dashes instead of underscores in target names.
-    platform = platform.replace('_', '-')
+    platformstr = platformstr.replace('_', '-')
     try:
         subprocess.run(
-            ['make', f'prefab-{platform}-{target.value}-build'], check=True
+            ['make', f'prefab-{platformstr}-{targetstr}-build'], check=True
         )
     except (Exception, KeyboardInterrupt) as exc:
         if str(exc):

tools/batools/pcommands2.py

@@ -204,7 +204,7 @@ def win_ci_install_prereqs() -> None:
 
     # We'll need to pull a handful of things out of efrocache for the
     # build to succeed. Normally this would happen through our Makefile
-    # targets but we can't use them under raw window so we need to just
+    # targets but we can't use them under raw Windows so we need to just
     # hard-code whatever we need here.
     lib_dbg_win32 = 'build/prefab/lib/windows/Debug_Win32'
     needed_targets: set[str] = {
@@ -256,11 +256,11 @@ def win_ci_binary_build() -> None:
 
 
 def update_cmake_prefab_lib() -> None:
-    """Update prefab internal libs for builds."""
+    """Update prefab internal libs; run as part of a build."""
     import subprocess
     import os
     from efro.error import CleanError
-    import batools.build
+    from batools.build import PrefabPlatform
 
     pcommand.disallow_in_batch()
 
@@ -275,14 +275,18 @@ def update_cmake_prefab_lib() -> None:
         raise CleanError(f'Invalid buildtype: {buildtype}')
     if mode not in {'debug', 'release'}:
         raise CleanError(f'Invalid mode: {mode}')
-    platform = batools.build.get_current_prefab_platform(
-        wsl_gives_windows=False
-    )
-    suffix = '_server' if buildtype == 'server' else '_gui'
-    target = f'build/prefab/lib/{platform}{suffix}/{mode}/libballisticaplus.a'
 
-    # Build the target and then copy it to dst if it doesn't exist there yet
+    # Our 'cmake' build targets use the Linux side of WSL; not native
-    # or the existing one is older than our target.
+    # Windows.
+    platform = PrefabPlatform.get_current(wsl_targets_windows=False)
+
+    suffix = '_server' if buildtype == 'server' else '_gui'
+    target = (
+        f'build/prefab/lib/{platform.value}{suffix}/{mode}/libballisticaplus.a'
+    )
+
+    # Build the target and then copy it to dst if it doesn't exist there
+    # yet or the existing one is older than our target.
     subprocess.run(['make', target], check=True)
 
     libdir = os.path.join(builddir, 'prefablib')
@@ -431,7 +435,7 @@ def wsl_build_check_win_drive() -> None:
         != 0
     ):
         raise CleanError(
-            'wslpath not found; you must run this from a WSL environment'
+            "'wslpath' not found. This does not seem to be a WSL environment."
         )
 
     if os.environ.get('WSL_BUILD_CHECK_WIN_DRIVE_IGNORE') == '1':